When making an X-ray exposure, it is known to place one or more individual lead pieces between the X-ray source and the X-ray sensitive film to block a selective portion of the X-rays imparted to the film and thereby prevent the X-rays from affecting the film over the portions of the film corresponding to the shape of the lead pieces. Typically, the lead pieces are taped in a stationary position at a location overlapping a corner of the film. The X-rays are substantially blocked over the portion of the film situated beneath the lead pieces, producing a clear or light white image on the X-ray exposure in a pattern corresponding to the X-ray pieces, with the portion of the X-ray exposure immediately surrounding the clear indicia not being blocked and therefore being dark. In this manner, the lead pieces form identifying indicia on the X-ray exposures.
For instance, to indicate on the X-ray exposure that it is a left side view in a particular shot, an L-shaped lead piece may be taped to the platen in which the film is disposed, at a location overlapping a corner portion of the X-ray sensitive film. This produces a clear L-shaped portion on the X-ray film when subjected to X-ray energy from the X-ray source, to readily identify that it is a left view in that particular X-ray exposure.
There are numerous shortcomings associated with employment of such lead markers in forming identifying indicia on X-ray film. Among these shortcomings is the toxicity of lead which may cause medical problems for persons frequently in contact with the lead. Hence, workers, who must mount and remove the lead markers to and from the film-receiving platen between each shot, and who store and clean the lead markers, are reluctant to handle the lead markers due to the medical risks they pose.
Still further, it is desirable to form thin indicia on the X-ray film since the indicia are substantially clear and, therefore, too wide or too large of such clear indicia let through too much light when observing the X-ray exposure with traditional back lighting. This results in a searchlight effect, with the back lighting shining virtually unimpeded through the large or wide clear portions of the film and shining into the viewer's eyes, and sometimes requiring the viewer to cover the indicia-bearing portion of the X-ray exposure when viewing the X-ray image. Methods for forming thin lead indica may require subjecting lead to high heat, such as in employment of laser processing, which produces toxic fumes, therefore making lead undesirable for production by such methods.
While it is possible to find a lead substitute for a small range of intensities of X-rays, there has not been an effective substitute for lead X-ray markers where the X-ray intensity varies considerably, e.g. from 8 milliamp-seconds to 300 milliamp-seconds at 25 KVA in mammographic X-rays of breasts for lumps. Small soft breasts may be X-rayed at the low end of this range. Breasts that have been subjected to radiation treatment have harder and more dense tissue requiring X-ray intensity in the upper end of this range. Materials and thicknesses that work well at the low end of the intensity range have not worked well at the high end of this intensity range. Thus, there is a need to find and develop an X-ray marker for forming identifying indicia on X-ray film when subjected to any of a wide range of intensity levels, which X-ray marker does not contain lead.
Furthermore, current markers must be taped in a desired position onto the platen in which the X-ray film is received to hold the markers in place during the X-ray exposure. Tape, which is currently employed to mount the lead markers to a platen, has been found to be a cumbersome and inaccurate mounting means. In many applications, several shots of a subject are required to be taken at different angles, and it is necessary to remove a previously-applied marker from the platen and tape a new marker to the platen between each different shot to identify each of the different angles. Considerable time is spent between each different X-ray exposure taping a plurality of different markers, suitable for properly identifying the particular X-ray exposure, to the platen. Also, it may be necessary to rotate the platen in any or each of three different planes between each of the different X-ray exposures, and the tape has been found to be an ineffective means of mounting the markers since it frequently allows the markers to shift or fall off during rotation of the platen. Accordingly, there is a need for markers which are easily mountable and detachable from a platen and will not slip during shifting of the platen.
Still further, it is necessary to frequently clean the markers. Current markers are difficult to clean due to their discontinuous surfaces, and the cotton used to wash the markers with alcohol often gets caught or snagged on the sharp corners of the markers. There is a need for a marker which meets the above requisites and which also is easy to clean repeatedly.